Definition
Quadrilateral_1-2.jpg
Quadrilateral is a 4-sided polygon





Properties


Angle Properties

Quadrilateral_2-3.jpg
There are 4 angles

1. *All angles add up to 360
Angle AQU + Angle QUD + Angle UDA + Angle DAQ = 360
71.32 + 81.94 + 105.12 + 101.62 = 360


This is the most important property of a quadrilateral for the following reasons:
- By knowing that all angles in a quadrilateral add up to 360, unknown angle measures can be easily solved
Example:
Example_2.jpg
Kite, a type of quadrilateral has one pair of opposite angles that are congruent (In this diagram Angle IKE & Angle ITE).
Given that Angle KIT is 80 degrees, and Angle KET is 60 degrees, we can find the measures of Angle IKE & ITE because we know that all angles of a quadrilateral must add up to 360 (kite is a quadrilateral).
Angle KIT + Angle KET + Angle IKE + Angle ITE = 360
Angle KIT + Angle KET = 80 + 60 = 140
360 - 140 = 220
Angle IKE + Angle ITE = 220
Angle IKE = Angle ITE
220 / 2 = 110
Angle IKE = 110
Angle ITE = 110